The present invention relates to a melt polymerization process for preparing resorcinol phthalate polyesters, wherein an ester interchange reaction takes place and product prepared therefrom.
In the past, polyesters have been prepared by a variety of methods including ester interchange, direct esterification, interfacial polymerization and acidolysis (see U.S. Pat. No. 4,011,199).
The stability of the reactants and the melt viscosity of the polyester prepared therefrom often play a dominant role in selecting a commercially acceptable manufacturing process. For example, polyesters of aliphatic and cycloaliphatic diols have viscosities that make these polyesters particularly suitable for commercial preparation using an ester interchange process. Polyesters prepared using aromatic diols, however, typically have such high melt viscosities that ester interchange cannot be used.
One particular method of achieving an ester interchange reaction is by a melt polymerization technique. This procedure is advantageous because it permits utilization of the free acid as opposed to the more expensive acid chloride required by certain other techniques. Further advantages of this technique lie in the ability to dispense with solvent recovery and acid neutralization procedures necessitated by the acid chloride route.
The melt polymerization procedures of the prior art, however, yield a commercially unacceptable product when applied to the preparation of a resorcinol phthalate polyester.
This results, in part, from the fact that resorcinol by itself does not react with phthalic acids in a melt process to yield a usable resorcinol phthalate polyester.
It has been observed that resorcinol phthalate polyesters in general are known as illustrated by W. Eareckson, Interfacial Poly Condensation X Poly Phenyl Esters, 40 J. Pol. Sci. 399-406 (1959); U.S. Pat. Nos. 3,160,602; 2,595,343; and 2,035,578; and British Pat. No. 863,704. The discussion of resorcinol-phthalate polyesters in the prior art, however, has typically centered on methods of making polyesters in general. Consequently, the description of specific resorcinol phthalate polyesters and the properties associated therewith have been of limited scope.
Thus, only resorcinol phthalate polyesters having either 100% isophthalic acid, 100% terephthalic acid, or a 50:50 molar ratio of a mixture of isophthalic and terephthalic acid appear to have been recognized and described in the art.
It has heretofore been unknown that only certain proportional isomer ranges of isophthalic and terephthalic acid are capable of yielding a melt processable polymer. It has also been unknown that the effective utilization of a melt polymerization process to prepare a resorcinol phthalate polyester is also contingent upon the employment of certain specified proportional acid isomer ranges.
It has been further observed that wholly aromatic polyesters may be prepared by an ester interchange reaction as illustrated by U.S. Pat. Nos. 3,160,604; 3,036,992; and 2,595,343.
It has been still further observed that a wide variety of catalysts have been considered for use in preparing wholly aromatic polyesters in general by an ester interchange reaction as illustrated by U.S. Pat. Nos. 3,824,213; and 3,651,041; and U.S. patent applicaton Ser. No. 789,374, filed Apr. 20, 1977, by G. Calundann, H. Davis, R. Gorman, and R. Mininni, entitled "Improved Melt Processable Thermotropic Wholly Aromatic Polyester Which Is Particularly suited for Fiber Formation."
For example, in the Calundann et al application, representative catalysts disclosed therein include dialkyl tin oxide, (e.g., dibutyl tin oxide), diaryl tin oxide, titanium dioxide, alkoxy titanium silicates, titanium alkoxides, the gaseous acid catalysts such as Lewis acids, hydrogen halides (e.g., HCl), alkali and alkaline earth metal salts of carboxylic acids (e.g., sodium acetate), etc.
It has not heretofore been known that alkali and alkaline earth metal acetate catalysts are especially suited for the preparation of a resorcinol phthalate polyester by the melt polymerization process described herein and that most of the conventional ester interchange catalysts such as the representative catalysts described above are unacceptable for this purpose.
It is, therefore, an object of the present invention to provide a process for the preparation of a melt processable resorcinol phthalate polyester by the melt polymerization of resorcinol diacetate and a phthalic acid or mixtures thereof.
It is another object of the present invention to provide a process for preparing a melt processable resorcinol phthalate polyester by the melt polymerization technique from resorcinol which is subsequently converted to a diacetate and a phthalic acid or mixtures thereof.
It is a still further object of the present invention to provide a melt processable resorcinol phthalate polyester.
These and other objects as well as the scope, nature and utilization of the invention will be apparent to those skilled in the art from the following description and appended claims.